[PATCH v6 17/21] x86/fpu: Add uabi_size to guest_fpu

Paolo Bonzini
2022-01-07T18:55:42Z

From: Thomas Gleixner <tglx@linutronix.de>

Userspace needs to inquire KVM about the buffer size to work
with the new KVM_SET_XSAVE and KVM_GET_XSAVE2. Add the size info
to guest_fpu for KVM to access.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Signed-off-by: Jing Liu <jing2.liu@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Message-Id: <20220105123532.12586-18-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/include/asm/fpu/types.h | 5 +++++
arch/x86/kernel/fpu/core.c | 1 +
arch/x86/kernel/fpu/xstate.c | 1 +
3 files changed, 7 insertions(+)

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index 3795d0573773..eb7cd1139d97 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -522,6 +522,11 @@ struct fpu_guest {
*/
u64 xfd_err;

+ /*
+ * @uabi_size: Size required for save/restore
+ */
+ unsigned int uabi_size;
+
/*
* @fpstate: Pointer to the allocated guest fpstate
*/
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 271fd5bc043b..de8e8c21f355 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -240,6 +240,7 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
gfpu->fpstate = fpstate;
gfpu->xfeatures = fpu_user_cfg.default_features;
gfpu->perm = fpu_user_cfg.default_features;
+ gfpu->uabi_size = fpu_user_cfg.default_size;
fpu_init_guest_permissions(gfpu);

return true;
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 0c0b2323cdec..10fe072f1c92 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1545,6 +1545,7 @@ static int fpstate_realloc(u64 xfeatures, unsigned int ksize,
newfps->is_confidential = curfps->is_confidential;
newfps->in_use = curfps->in_use;
guest_fpu->xfeatures |= xfeatures;
+ guest_fpu->uabi_size = usize;
}

fpregs_lock();
--
2.31.1